TORONTO - The proportion of Canadian adults with high blood pressure has remained virtually unchanged over the last 15 years, although a much higher percentage are managing to keep the condition in check, a survey of Ontario residents suggests.
A 2006 study of more than 2,500 Ontario adults found one in five had high blood pressure and of those, 66 per cent were receiving treatment that kept the condition well-controlled.
That's in huge contrast to a similar survey in 1992, when only 16 per cent of adult Canadians had their hypertension under control with treatment, said principal investigator Dr. Frans Leenen of the University of Ottawa Heart Institute.
"We know that high blood pressure should be treated and that it is extremely beneficial for the individual that blood pressure is being treated properly," Leenen, the institute's director of hypertension, said from Ottawa.
High blood pressure, also known as hypertension, is diagnosed when systolic blood pressure reaches 140 and diastolic pressure 90. A blood pressure reading of 120/80 is considered ideal.
Leenen, whose study is published in Tuesday's edition of the Canadian Medical Association Journal, said treatment and control rates in Ontario are likely representative of Canada overall.
Still, that means more than a third of Canadian adults are not properly dealing with high blood pressure, which can lead to stroke, heart attack and kidney disease, all of which can result in premature death.
Among those identified with inadequate blood pressure management, 19 per cent were completely untreated and of those, 14 per cent were unaware they had hypertension at all. Fifteen per cent were receiving treatment but were not adequately controlled.
"So there is still clearly room for improvements in better management, but it is getting there," Leenen said.
There was more bad news contained in the results of the study, which included measuring participants' blood pressure and body mass index (BMI, a ratio of height and weight).
"If you look at the people 60-plus, for example, overall 51 per cent have hypertension," said Leenen, noting that among South Asians (from India, Pakistan, Sri Lanka and Bangladesh), 75 per cent in that age group had high blood pressure, "which is really, when you think of it, a staggering number."
More than 60 per cent of people of East Asian descent (Chinese and Indonesian, for example) and blacks aged 60 and older also had chronically elevated blood pressure.
Prevalence among blacks is of particular concern because they tend to develop the condition much earlier in life; in the 40 to 59 age range, more than half have hypertension, Leenen said.
"And that, of course, puts them at a significantly higher risk of developing a stroke or heart attack earlier in their life."
Leenen said a genetic predisposition can make some people susceptible to high blood pressure, but lifestyle also plays a key role.
Being overweight or obese can drive the development of hypertension, along with being physically inactive, smoking tobacco and eating too much salt.
Those who are obese, with a BMI of 30 or beyond, have a 3.5-fold higher risk of hypertension compared to those with a BMI under 25, the study shows.
Commenting on the study, Dr. Sheldon Tobe said the fact that two-thirds of those with high blood are controlling their condition puts Ontario, and likely Canada as a whole, "ahead of every other jurisdiction in the world."
"People are becoming more aware of the importance of being treated for high blood pressure, and it's starting to work," said Tobe, a kidney specialist at Sunnybrook Health Sciences in Toronto and spokesman for the Heart and Stroke Foundation, which funded the study.
In two companion studies published in CMAJ, researchers at the Institute for Clinical Evaluative Sciences (ICES) used Ontario health records to determine changes in rates of people actually being diagnosed with hypertension and deaths resulting from the condition.
The studies found that over time, more adults with high blood pressure were getting diagnosed - from 153 per 1,000 in 1995 to 245 per 1,000 in 2005, a relative rise of 60 per cent.
Death rates from hypertension-related diseases fell 15.5 per cent during the same period, said principal author Dr. Karen Tu, a Toronto family doctor and an ICES scientist.
The authors speculate that the drop in the death rate is partly due to improved detection and control of high blood pressure.
In a related commentary, Drs. Sailesh Mohan and Norm Campbell of the University of Calgary say the contrast in hypertension prevalence rates between Leenen and Tu's studies likely result in part from the sources of their data.
Health-record data used by Tu's group may overestimate the prevalence of high blood pressure after 1999, they say, because of the introduction of the Canadian Hypertension Education Program, which increased awareness among physicians and the public.
"The sharp increase in the incidence of hypertension after 1999 reported by Tu and colleagues coincides with and probably represents an increase in the detection of hypertension rather than a true increase in its incidence," they write.
Still, Leenen's finding that one in three people with hypertension did not have it under control "clearly indicates that more needs to be done," Mohan and Campbell stressed.
"Although hypertension is preventable, it is estimated that the condition will develop in 90 per cent of Canadians. These are important challenges, and there is much that can be done to improve health through prevention and control of hypertension."
